Pig injectors having magazines for storing several pigs have been known at least since issuance of Canadian patent no. 649,678 and U.S. Pat. No. 3,028,996 by the inventor of the present invention. In these patents there is described a pig injector for injecting spherical pigs into a pipe, in which the pigs fall from a magazine into a T section extending perpendicularly from the pipe. The pigs may then be injected by a piston and rod arrangement into the pipe.
There is also known a multiple pig launching system made by ITAG. In this design, plural spherical pigs are stored in a magazine and released, one at a time, by a solenoid controlled finger into a rotatable pig launching valve. The pig launching valve has a ball with an interior bore and stops at the end of the bore for preventing the pig from moving the wrong way once the pig is placed in the pipe.
A further design for the launching of spherical pigs into a pipe is shown in U.S. Pat. No. 4,435,872 of Leikam. This design allows for the introduction of pigs without impeding flow of fluid in the pipe.
None of these designs is suitable for the introduction of elongate pigs into a pipe, and they require somewhat complicated metering systems, so that only one pig at a time is injected into the pipe. The present invention provides in accordance with one aspect of the invention a pig injector for injecting multiple elongate pigs and in accordance with another aspect a simplified metering design. An indicator of pig level in the magazine is also provided.